Organic light emitting display and method of fabricating the same

ABSTRACT

An organic light emitting display (OLED) and a method of fabricating the same are provided. The method includes forming the OLED having upper and lower substrates that emit different colors from each other, and coupling the upper and lower substrates together.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/283,933, filed on Nov. 22, 2005, and claims priority to andthe benefit of Korean Patent Application No. 10-2004-0096595, filed Nov.23, 2004, which are hereby incorporated by reference for all purposes asif fully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic light emitting display(OLED) and a method of fabricating the same and, more particularly, toan OLED including first and second substrates attached with each other,each of which emits different colors.

2. Discussion of the Background

Generally, a cathode ray tube (CRT) is often used for a TV monitor,measuring equipment, or an information terminal. However, the CRT is notused with small and lightweight electronic products due to its weightand size.

Thin and lightweight flat panel displays (FPD) are being substituted forCRTs. Such flat panel displays generally include a liquid crystaldisplay (LCD), an OLED, etc.

A FPD may be a passive matrix FPD or an active matrix FPD according toits driving method.

The active matrix FPD includes a thin film transistor (TFT) substratehaving a TFT formed therein, and red, green and blue light emittingdiodes.

The active matrix FPD generally include at least two TFTs, i.e., aswitching TFT and a driving TFT, a capacitor, and a light emitting diode(LED) in each pixel.

However, with top and bottom emitting active matrix FPDs, since the TFTand the capacitor occupy a relatively large area, less space isavailable for forming the LED, which reduces the aperture ratio.

Additionally, in order to increase the mobility of a TFT active layer,the TFT's size may be increased, which means it occupies a larger areain the pixel.

FIG. 1 is a cross-sectional view of a conventional OLED.

Referring to FIG. 1, a buffer layer 110 having a predetermined thicknessis formed on a transparent insulating substrate 100 having red (A),green (B) and blue (C) pixel regions. The buffer layer 110 preventsimpurities from the transparent insulating layer 100 from beingintroduced into the TFT, which is subsequently formed.

Next, polysilicon layer patterns 120 are formed on the buffer layer 110,and impurities are injected into both sides of the polysilicon layerpatterns 120, thereby forming source and drain regions 122 and 124, andchannel regions 126 between the source and drain regions, in each pixelregion A, B and C.

Next, a gate insulating layer 130 is formed on the entire surface of theresultant structure, and gate electrodes 132 are then formed tocorrespond to the channel regions 126 of the polysilicon layer patterns120.

Next, an interlayer insulating layer 140 is formed on the entire surfaceof the resultant structure, and the interlayer insulating layer 140 andthe gate insulating layer 130 are etched to form contact holes 142,which expose the source and drain regions 122 and 124. Source and drainelectrodes 150 and 152 are then formed to be connected with the sourceand drain regions 122 and 124, respectively, through the contact holes142.

Next, a passivation layer 160 and a planarization layer 170 are formedon the entire surface of the resultant structure.

The passivation layer 160 and the planarization layer 170 are thenetched to form via-holes 172, which expose the drain electrodes 152.

Next, pixel electrodes 180 are formed to be connected with the drainelectrodes 152 through the via-holes 172 in each pixel region A, B andC. The pixel electrode 180 may be a reflective electrode.

Portions of the pixel electrodes 180 are then exposed on the entiresurface of the resultant structure to form a pixel defining layerpattern 182 for defining an emission region.

Next, an organic layer 190, which includes at least an emission layer,and an opposite electrode 192 are formed on the entire surface of theresultant structure. The organic layer 190 may include an emission layerthat emits blue or white light.

A transparent passivation layer (not shown) is then formed on theopposite electrode 192.

A sealing substrate 200 is adhered corresponding to the transparentinsulating substrate 100 to complete the OLED. A moisture absorbingagent may be formed on the sealing substrate 200.

As described above, since the conventional OLED includes a plurality ofpixel regions formed in one insulating substrate, as higher resolutionand brightness are required, pixel patterning may become difficult.Further, with the active matrix OLED, the aperture ratio and the OLED'slifespan may decrease since the TFT and capacitor are formed in eachpixel.

SUMMARY OF THE INVENTION

The present invention provides an organic light emitting display (OLED)and a method of fabricating the same that may increase an aperture ratioand facilitate the manufacture of a large-sized OLED by forming firstand second substrates, which emit different colors of light, andadhering the first and second substrates to each other.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

The present invention discloses an OLED including a first substrate anda second substrate coupled with each other. The first substrate includesa first pixel electrode, a first organic layer having at least anemission layer, and a first opposite electrode, and the second substrateincludes a second pixel electrode, a second organic layer having atleast an emission layer, and a second opposite electrode. Together, thefirst and second substrates have first, second and third pixel regions.

The present invention also discloses a method of fabricating an organiclight emitting display including forming a first pixel electrode on afirst substrate having at least two pixel regions, forming a firstorganic layer having at least an emission layer on the first pixelelectrode, and forming a first opposite electrode on the first organiclayer. A second pixel electrode is formed on a second substrate havingat least one pixel region, a second organic layer having at least anemission layer is formed on the second pixel electrode, and a secondopposite electrode is formed on the second organic layer. The first andsecond substrates are coupled with each other.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention, andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a cross-sectional view of a conventional organic lightemitting display.

FIG. 2 is a cross-sectional view of an organic light emitting displayaccording to an exemplary embodiment of the present invention.

FIG. 3A, FIG. 3B, and FIG. 3C are layouts of an organic light emittingdisplay according to exemplary embodiments of the present invention.

FIG. 4 is a schematic cross-sectional view of an organic light emittingdisplay according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure is thorough, and will fully convey the scope of theinvention to those skilled in the art. In the drawings, the size andrelative sizes of layers and regions may be exaggerated for clarity.

It will be understood that when an element such as a layer, film, regionor substrate is referred to as being “on” another element, it can bedirectly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present.

FIG. 2 is a cross-sectional view of an organic light emitting display(OLED) according to an exemplary embodiment of the present invention,and FIG. 4 is a schematic cross-sectional view of an OLED according toan exemplary embodiment of the present invention, which will bedescribed in conjunction with each other.

Referring to FIG. 2, a first substrate 300 and a second substrate 400face each other. The first substrate 300 includes a thin film transistor(TFT) having a gate electrode 332, a source electrode 350 and a drainelectrode 352, a pixel electrode 380, an organic layer 390 having atleast an emission layer, and an opposite electrode 392. The secondsubstrate 400 includes a TFT, a pixel electrode, an organic layer havingat least an emission layer, and an opposite electrode. The firstsubstrate 300 includes two pixel regions, and the second substrate 400includes one pixel region.

Hereinafter, a method of fabricating an OLED will be described withreference to FIG. 2.

A buffer layer 310 having a predetermined thickness is formed on thefirst substrate 300, which has at least two pixel regions. The bufferlayer 310 prevents impurities leaked from the first substrate 300 frombeing introduced into a subsequently formed TFT.

Polysilicon layer patterns 320 may then be formed on the buffer layer310. Impurities are injected into both sides of the polysilicon layerpatterns 320, thereby forming source and drain regions 322 and 324, andchannel regions 326 between the source and drain regions, in each pixelregion.

A gate insulating layer 330 may then be formed on the entire surface ofthe resultant structure, and gate electrodes 332 may be formed tocorrespond to the channel regions 326 of the polysilicon layer patterns320.

An interlayer insulating layer 340 may then be formed on the entiresurface of the resultant structure, and then the interlayer insulatinglayer 340 and the gate insulating layer 330 are etched to form contactholes 342, which expose the source and drain regions 322 and 324. Sourceand drain electrodes 350 and 352 may then be formed to be electricallycoupled with the source and drain regions 322 and 324, respectively,through the contact holes 342.

A passivation layer 360 and a planarization layer 370 may then be formedon the entire surface of the resultant structure.

Then, the passivation layer 360 and the planarization layer 370 may beetched to form via-holes 372, which expose the drain electrodes 352.

Next, pixel electrodes 380 may be formed to be electrically coupled withthe drain electrodes 352 through the via-holes 372 in each pixel region.The pixel electrode 380 may be a reflective electrode.

Portions of the pixel electrodes 380 are exposed on the entire surfaceof the resultant structure to form a pixel defining layer pattern 382,which defines an emission region.

Next, an organic layer 390, having at least an emission layer, may beformed on the entire surface of the resultant structure. Here, theemission layer may be formed in the two pixel regions of the firstsubstrate 300 using a fine metal mask (FMM) by each color, or a blueemission layer may be formed on the entire surface of the resultantstructure after forming a red or green emission layer using the FMM.

Next, an opposite electrode 392 may be formed on the organic layer 390.The opposite electrode 392 may be a transparent electrode.

Similarly, the second substrate 400, which may include one pixel region,may be formed using the above method. Unlike the pixel electrode 390formed on the first substrate 300, the pixel electrode formed on thesecond substrate 400 may be a transparent electrode, and the oppositeelectrode 492 may also be a transparent electrode. This is because thepixels formed on the first substrate 300 emit light through the secondsubstrate 400. Additionally, the organic layer formed on the secondsubstrate 400 may be formed on the entire surface of the substratewithout using the FMM. At this time, although it is possible to form redand green emission layers in each emission region of the first substrate300, when the blue emission layer is used as a common layer, the numberof alignments may be reduced since the red or green emission layer mayoverlap the blue emission layer. In this case, the number of times theFMM is used may be reduced by one. As described above, by separatelyforming the pixel regions in the first and second substrates 300 and400, it may be possible to increase an aperture ratio at least threetimes in the case of the first substrate 300, and at least nine times incase of the second substrate 400.

As shown in FIG. 4, the first and second substrates 300 and 400 may becoupled with each other using an adhesive agent 500 and a spacer 700 isformed between the first and second substrates 300 and 400. At thistime, an organic insulating layer may be arranged between the first andsecond substrates 300 and 400. Additionally, a driver integrated circuit(IC) 600 may be attached to the periphery of one of the first and secondsubstrates 300 and 400. For example, FIG. 4 shows the driver IC 600attached to the first substrate 300. The first and second substrates maybe electrically connected to each other using an anisotropic conductivefilm having conductive particles between the first and second substrates300 and 400. FIG. 4 also shows, as an example, the second substrate 400including the red (A) pixel region and the first substrate 300 includingthe green (B) pixel region and the blue (C) pixel region.

FIG. 3A, FIG. 3B and FIG. 3C are views of layouts of an OLED accordingto exemplary embodiments of the present invention, representing colorsof emission layers to be formed on the first and second substrates.

First, FIG. 3A and FIG. 3B show red R, green G and blue B pixel regionsarranged in the first and second substrates in a divided manner. In thisprocess, the first substrate may be arranged at a lower position, andthe second substrate may be arranged at an upper position.

Referring to FIG. 3A, the first substrate includes the blue pixel regionB and the green pixel region G, and the second substrate includes thered pixel region R.

Referring to FIG. 3B, the first substrate includes the blue pixel regionB and the red pixel region R, and the second substrate includes thegreen pixel region G.

FIG. 3C illustrates when the first and second substrates include red R,green G, blue B, cyan C, magenta M and yellow Y pixel regions. Here, acyan pixel C comprises green and blue pixels G and B, a magenta pixel Mcomprises red and blue pixels R and B, and a yellow pixel Y comprisesred and green pixels R and G. Therefore, as shown in FIG. 3C, the firstsubstrate sequentially includes green G, blue B, blue B, red R, red R,blue B, blue B and green G pixels, and the second substrate sequentiallyincludes red R, green G, green G and red R pixels. Each pixel may beseparately driven, and the cyan, magenta and yellow pixels may beimplemented by driving pixels corresponding to each color.

As described above, exemplary embodiments of the present invention mayreduce the deposition number of the organic layer using the FMM andincrease the aperture ratio to lengthen the lifespan of the OLED byseparately forming the pixels on the two substrates by each color.Further, it may be possible to facilitate the manufacture of alarge-sized OLED due to reduced process time by means of the reducednumbers of alignment.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A method of fabricating an organic light emitting display,comprising: forming a first pixel electrode on a first substrate, thefirst substrate comprising at least two pixel regions; forming a firstorganic layer having at least an emission layer on the first pixelelectrode; forming a first opposite electrode on the first organiclayer; forming a second pixel electrode on a second substrate, thesecond substrate comprising at least one pixel region; forming a secondorganic layer having at least an emission layer on the second pixelelectrode; forming a second opposite electrode on the second organiclayer; and coupling the first substrate and the second substrate witheach other.
 2. The method of claim 1, further comprising: forming atleast one thin film transistor between the first substrate and the firstpixel electrode; and forming at least one thin film transistor betweenthe second substrate and the second pixel electrode.
 3. The method ofclaim 1, wherein the first organic layer is formed in the at least twopixel regions using a fine metal mask.